This application relates to an application entitled xe2x80x9cMULTI-SWEEP METHOD AND SYSTEM FOR MAPPING TERRAIN WITH A WEATHER RADAR SYSTEMxe2x80x9d by Daniel L. Woodell, and also relates to another application entitled xe2x80x9cMETHOD AND SYSTEM FOR DETECTING TURBULENCE WITH REDUCED ERRORS RESULTING FROM VERTICAL SHEAR COMPONENTSxe2x80x9d, by Daniel L. Woodell, Roy Robertson, and Ying C. Lai; and further relates to an application entitled xe2x80x9cMETHOD AND SYSTEM FOR SUPPRESSING GROUND CLUTTER RETURNS ON AN AIRBORNE WEATHER RADARxe2x80x9d by Daniel L. Woodell, all filed on even date herewith and assigned to a common assignee, which applications are incorporated herein in their entirety by this reference.
The present invention generally relates to radars, and more particularly relates to weather radars, and even more particularly relates to methods and systems for using multiple sweeps to improve performance of weather radars.
In recent years, avionics engineers have endeavored to improve safety of flight and reduce pilot workload. Often, it is difficult to simultaneously achieve these two desirable results. One example of this is in the area of weather radar where pilots have had long-standing problems with discerning ground clutter from weather returns.
Pilots have frequently used an antenna tilting technique where the tilt angle of the transmitted radar beam is adjusted in flight to provide two different views from the radar. The term xe2x80x9cbeamxe2x80x9d is used herein to refer to the entire transmission area during a single azimuthal sweep of the antenna at a single tilt angle. One tilt angle might be directed to be slightly above the radar horizon. This tilt angle, in conjunction with known ground clutter suppression techniques, is often used to deliver an image with the best elimination of ground clutter. However, this tilt angle has limitations in effective range. To overcome these range limitations, the pilot may then adjust the radar beam downward so as to just graze the ground at the radar horizon or involve the ground at some point nearer the aircraft. The pilot must then mentally process the information displayed and make some attempts to determine which displayed returns are a result of ground clutter and which are actual weather returns.
While these pilot-controlled tilt adjustments have been used extensively in the past, they do have some drawbacks. First of all, leaving the radar beam above the radar horizon compromises the primary function of the radar, which is weather detection. A beam directed at too high of an angle will, due to the curvature of the earth, miss some storms at long range. It will also not detect some weather at short and mid ranges as well. For example, a beam directed at too high of an angle will not detect xe2x80x9coverflightxe2x80x9d weather. This term should be understood to be weather which, while not in the path of the aircraft, the plane will fly over and which can produce turbulent air in the flight path. Additionally, the tops of storms are often comprised of moisture in the form of ice crystals, which generally are known to deliver weaker radar returns than liquid moisture usually found at lower altitudes. Addressing these limitations requires the pilot to manually adjust the tilt angle of the transmitted radar beam to several different tilt angles to get a complete picture of the weather situation and hazards. This can be a significant effort. (Note: auto-tilt radars have been used to help reduce pilot workload relating to finding the proper angle above the radar horizon.) As mentioned above, if the beam is too far above the radar horizon, it dramatically affects both the long and short-range limits of the radar. If it is below the radar horizon, then it will produce heavy ground clutter. More importantly, these attempts to improve effective range, (whether by manual tilt by the pilot or auto-tilt by the radar system), have increased pilot workload, in that the pilot is now required to view multiple radar images and mentally process the differences in the images to determine what is and is not ground clutter. This process is time consuming and is a potential source of pilot error, especially for inexperienced and fatigued pilots, and for pilots busy with other important piloting tasks.
Recently, weather radars have been introduced which utilize on-board position determination equipment, such as GPS, and terrain databases to automatically control the tilt angle of the radar. For example, when such an aircraft approaches a mountain, the system, in an attempt to limit ground clutter, limits the tilt angle of the weather radar to only beams which are above the mountains. The use of only these higher tilt angles is effective at reducing ground clutter, but only with the drawbacks discussed above.
Consequently, there exists a need for improved methods and systems for detecting and displaying weather information in an efficient manner.
It is an object of the present invention to provide a system and method which enhances safety of flight.
It is a feature of the present invention to utilize a weather radar which. uses multiple sweeps to generate a single weather display image to the pilot.
It is an advantage of the present invention to achieve improved efficiency in interpreting the significance of returns displayed on a weather radar display.
It is another advantage of the present invention to increase the range of displayed weather information.
It is yet another advantage of the present invention to increase the awareness of the pilot of short-range and overflight weather conditions.
It is another advantage to reduce pilot workload required to derive weather hazard information from the radar and reduce training required for pilot operation and use of the radar system.
The present invention is an apparatus and method for detecting and displaying weather information which is designed to satisfy the aforementioned needs, provide the previously stated objects, include the above-listed features, and achieve the already articulated advantages. The present invention is carried out in a manner that utilizes multiple scans or antenna sweeps, each at an optimal tilt setting for a selected portion of the radar""s surveillance range, that are then used to generate a single image of weather information.
Accordingly, the present invention is a system and method including a weather radar detection, processing and display apparatus which uses information from multiple scans to generate a single displayed weather information image.